Fire doors are provided in buildings to prevent the spread of fires from one portion of the building to other portions. Various types of fire doors are provided to close different kinds of openings generally found in buildings. For example, for a vertical opening having a relatively short width in relation to its height, a vertical fire door is provided which can close in the direction from top to bottom, as shown in FIG. 14, referred hereinafter as a vertically closing fire door. Alternatively, as shown in FIG. 15, a fire door can be arranged to close in the direction from the bottom of the opening to the top, referred to hereinafter as an inverted vertical closing fire door. For a vertical opening that has a relatively large width or that is irregularly shaped, a fire door is provided which closes from side to side, as shown in FIG. 13, referred hereinafter as a side closing fire door. To enclose an area where there is an opening in the floor, such as a stairway or escalator, a horizontal fire door is provided, as shown in FIGS. 1 and 2.
Heretofore the inverted vertical fire door, the side closing fire door and the horizontal fire door each required an auxiliary power source, such as a battery backup system, auxiliary generator or the like, to supply energy to a motor to close such doors. However, in the event of a fire, such auxiliary power sources are apt to be damaged due to extreme heat, rendering such inverted vertical, side closing and horizontal fire doors inoperative. Accordingly, fire codes have been promulgated in the United States that require fire doors to close in response to a fire without the use of an auxiliary power source. In view of the above discussed problems, the inverted vertical, side closing and horizontal fire doors have not been generally used in the United States. On the other hand, the vertical fire door generally relies on gravity acting on the weight of the door to assist in closing and therefore it does not require an auxiliary power source.
U.S. Patent application No. 07/859,833, U.S. Pat. No. 5,203,392 is an example of a vertical fire door, the disclosure of which is incorporated herein by reference. Such a fire door comprises a plurality of interconnected relatively pivotal horizontal slats and a pair of vertical guides positioned on either side of the curtain for guiding the curtain for vertical movement between a first or raised position and a second or lowered position. A mechanism is further provided for regulating the speed of the raising and lowering of the fire door. Under normal ambient conditions, the mechanism holds the door open; however, if a fire occurs the mechanism releases the fire door permitting the regulated closing of the door to secure a doorway and to prevent the fire from spreading from one location to another. This application, however, does not attempt to solve the problem of other types of fire doors previously discussed.
U.S. Pat. No. 4,754,795 to Garrod is directed to a rolling shutter for closing a doorway from a side-to-side direction, the disclosure of which is incorporated herein by reference. The Garrod device comprises a roller mounted vertically and comprises an inner shaft and an outer tube. A shutter curtain is adapted to be wound on the outer tube in a withdrawn condition, and a guide means is arranged to support the weight of the curtain in the extended condition and comprises a top track. The roller includes a resilient tensioning means for tensioning the curtain and provides a substantially constant tensioning force on the curtain throughout its travel between the withdrawn and extended conditions. The curtain is opened and closed by an electrical motor.
British Patent Application 2,172,327 also to Garrod is directed to a similar roller shutter as descried in U.S. Pat. No. 4,754,795, but is arranged for closing and opening in a substantially horizontal direction. This apparatus also requires an electric motor for opening and closing the curtain.
Since both devices to Garrod require an electric motor to open and close the door, neither one solves the above described problem.